Photochemistry and in vitro phototoxicity studies of levomepromazine (methotrimeprazine), a phototoxic neuroleptic drug.

The neuroleptic drug levomepromazine (1, previously known as methotrimeprazine) is photolabile under UV-A and UV-B light in aerobic conditions. Irradiation of a methanol solution of this drug produces one photoproduct, resulting from the oxidation of 1 to its sulfoxide parent. It is demonstrated that photodegradation occurs via type II mechanism involving irreversible trapping of self-photogenerated singlet molecular oxygen. 1 shows a photohemolytic effect on human erythrocytes and photoinducers lipid peroxidation.